Heat exchanger



March 24, 1 959 s. A. DOMAL HEAT EXCHANGER 2 Sheets-Sheet 1 Filed 001:. 31, 1955 March 24, 1959 s. A; DOMAL 4 2,878,656

HEAT EXCHANGER Filed Oct. 31, 1955 2 Sheets-Sheet 2 jZ cUZZZg/ Q. Dame Ll W /5mm Q2 United States Fatent HEAT EXCHANGER Stanley A. Domal, Wyandotte, Mich., assignor to Borg- Warner Corporation, Chicago, 111., a corporation of Illinois v v Application October 31, 1955, Serial No. 543,770

1 Claim. (Cl. 62-290) This invention relates to air conditioners and more particularly to the construction and design of heat exchangers for air conditioners.

At the outset, it is Well to point out that the use of t the language air conditioner" hereinafter is intended to embrace units which condition air by heating as well as by cooling. The term heat exchanger is intended to include structures embracing a plurality of core tubes or conduits making up what is commonly termed a primary heat transfer element through which fluid, either hot. or cold, may be forced for the purpose of encouraging the transfer of heat from the primary element to a fin or radiation structure commonly called a secondary" heat transfer element.

A particular object of the present invention is the provision of a heat exchanger having a favorable ratio of primary heat transfer surface with respect to the secondary heat transfer surface.

Another object of the present invention is the provision of a heat exchanger having a parallel flow path in contra-distinction to a tortuous or serpentine flow path;

Another object of the present invention is the pro-i vision of a heat exchanger developing a minimum resistance to fluid flow through the core tubes thereof 40 between the inlet and outlet sides of the core tubes for,

thus developing a relatively low pressure differential A still further object of the present invention is the' provision of a small, compact yet strong heat exchanger especially suitable for use in an air conditioner of the type adapted to be recessed in the walls of a building andoperable to heat the building in the winter season and' cool the building during warm weather.

A further object of the present invention is the pro-- vision of a'heat exchanger having closed side walls integral therewith so as to form a cowling or shroud around the core tubes and having an air inlet face and an air discharge face; the structure of the heat exchanger lend-' ing itself to flush mounting upon a wall of a casing having an opening therein of generally the same size and configuration as the inlet face of the heat exchanger.

A still further object of the present invention is the" p im yr n having a d h r e p s mm t se r,

6 ice ing with the discharge line directly through the opening in the secondary pan.

A heat exchanger embodying certain principles of I the present invention may include a plurality of generally parallel conduits, a first header communicating with and supporting corresponding ends of said parallel conduits and a second header spaced from the first header" and communicating with and supporting the other ends of said parallel conduits, said second header being divided into an inlet chamber and an outlet chamber, walls joining the ends of the headers so as to form a box-like", structure therewith, a plurality of spaced fins disposed transversely of said parallel conduits so as to form a" plurality of elongated air passageways through the box and transversely of said conduits, a primary condensate drain pan and a secondary condensate drain pan spaced from the primary pan, both pans having discharge openings therein, the discharge openings of the primary pan communicating with the corresponding opening of the secondary pan.

Other objects and features of the present invention will become more apparent from the following 'specificationand drawings wherein:

Fig. 1 is an elevational view of a portion of an air conditioner with which the heat exchanger of the present invention may be associated and showing to advantage the disposition of the primary and secondary condensate drain pans;

' -Fig. 2 is a sectional view, somewhat enlarged, of a portion of Fig. 1 as viewed in the plane of the line 2 2, for convenience the heat exchanger is shown in the tical position; v

Fig. 3 is a section of Fig. 2 as viewed in the plane of the line 33 and showing to advantage the disposition of wall or partition. The housing B is compartmented such that a fan (not shown) disposed behind a suitable filter the heat exchanger core elements and the configuration and structure of the headers;

Fig. 4 is anenlarged'view of the right end of the heat exchanger of Fig. 1 showing to advantage the actual disposition of the heat exchanger within the air conditioner as well as the relationship between the primary and'sec ondary drain pans; and

Fig. 5 is a front view of a portion of Fig. l som ewha'tt enlarged.

Referring now to Fig. 1 there is shown aportion of 4 an air conditioning unit indicated generally by the reference character A with the front grill or'cover removed. In general, the unit A comprises a rectangular metallic housing B suitably disposed between the studs C of a D encourages air to be drawn inwardly through the filter thence upwardly through suitable conduits in the back side of the housing to a vertical partition E. The

partition' E is formed with a generally rectangular open-1 ing E whose marginal regionscontact the edges of abox-like shroud which in turn supports and forms a part of a'heat exchanger F. Suitable fluid connections G are-provided to the core of the heat exchanger so as to.- provide a fluid flow path therethrough.

rangement of the heat exchanger F it is apparent that room temperature air flows into the housing B through the filter D thence upwardly along the rear wall of the housing and is thereafter channeled outwardly through the heat exchanger and returned to the room.

Having described a particular environment or setting within which'heat exchanger embodying the principles of the present invention may be utilized a more detailed description of the invention will now be undertaken. In Figs. 2 and 3 there is shown a plurality dof con- Patented Mar. 24,1959

ver'

In such an ar-'-.

duits having a generally rectangular configuration in cross section and disposed generally parallel to one another. The conduits 10 may be referred to hereinafter as core tubes and may be formed of any suitable metallic material such as copper or brass having a relatively high co-efficient of heat transfer.

The coretubes 10; are supported: at. the ends thereof;

by engagement with elongated slots 11 formed in azigzag or staggeredfashion. (Fig. 2) in theinner walls 12 and 13 of'the header members 14 and 16 respectively; Since the headers. are in effect tanks or reservoirs for fluid it necessarily follows that the joints between the periphery of the. various core tubes 10 and the walls 12v and 13 be sealed and made water tight as by brazing or by'a suitable tinning operation. As is apparent in Figs. 2

and}, the wall 12 is formed with a transverse rib orprotuberance which serves'to divide the header 14 in cooperation with shells,17 and 18 into an inlet chamber 19 and a discharge chamber 21. It is noted that the inlet chamber communicates with one group of core tubes indicated generally by the reference numeral 22 while the discharge chamber communicates with the group of core tubes indicated by the reference numeral 23. The inlet chamber 19 is provided with an opening 24 through which hot or cold water may be introduced from a remotely located hot and/or cold water supply. Corre-, spondingly the discharge chamber 21 is similarly fitted with any opening 26 which also communicates with the remotely located chiller and/or hot water supply. The discharge chamber 21 is also fitted with a vent, plug 21' which is removable to void the heat exchanger. of, entrapped air.

The header 16 is enclosed by the engagement ofan.

outer wall 27 which with the inner wall 13 comprises a single compartment 25 communicating with all core tubes 10. The wall 13 is sealed and makes a water tight connection with the periphery of the core tubes and the outer wall 27 as by brazing or tinning.

It is, well to point out that hereinafter, particularly in the claims to the present invention the core tubes collectively may be referred to as denoting a primary heat transfer surface. That is the portions of the core: tubes 10 disposed between the headers represent a medium through which there may be thermal conductivity by virtue: of the passage of hot or cold fluid through the interior of the tubes.

Disposed transversely of the core tubes and neatly encircling the outer periphery of each core tube are a -plurality of generally parallel foils or fins 10' which may be collectively referred to as a secondary heat transfer surface. The fins are made, of a relatively thin metallic material such as copper or bronze and may be corrugatedor crimped lightly so as to form slight grooves extending alonggthe length of the fins and interrupted.

by the core tubes 10. The fins are positioned on the core tubes by the. engagement of a, skirt portion 28 formed integral with the fins. The skirt portion 28. defines a slot through which the core tubes may be threaded prior to. fastening the headers to the core. tubes. the fins 10 are relatively pliable because of their. thin construction the skirt portion 28 thereof may be crimped around the core tube thus holding the fin in; position.

The .top side of the. heat exchanger is enclosed by a- Sincev Another purpose for the coplanar edge structure is to facilitate thermally insulating the heat exchanger-from the supporting, apertured wall by disposing a gasket or ring of suitable insulating material between the coplanar edge structure and the marginal regions of the apertured supporting wall. Such a gasket will, of course, further seal the edge structure to the supporting wall.

The lower wall 37 is further formed with a gradually deepening recess 38, hereinafter referred to as a primary condensate drain pan, having anopening 39 at the deepest portion thereof. The purpose. for this configuration of the bottom side of the heat exchanger is to provide a receptacle for the accumulation of condensate whichmaking a minimum or substantially no contact with the.v secondary pan and thence to a suiable drain by means of.

aplastic drain line or hose 42.

By providing the spaced primary and secondary drain. pans. 38 and 40' respectively a serious sweating problem. has beenvovercome.v Prior to the use of the drain pan. 38, relatively large quantities of condensate accumulat-- ing upon the primary and secondary heat transfer surfaces of the heatexchanger were permitted to drip downwardly; directly uponthe pan 40. This cold condensate chilled the pan 40- to the extent that moisture laden warm air entering the air conditioner through thefilter D.

condensed upon the underside of the secondary pan. This condensate ultimately dripped downwardly upon the fan motor and its electrical. wiring damaging these elements. if not rendering the air conditioner completely inoperative.

By forming the primary pan 38 integral with the heat exchanger the condensate originating upon the primary and secondary heat transfer surfaces is kept from spreading over the pan 40 and is directed through the aperture 41. into the plastic drain tube 42. Thus the condensate makes. substantially no contact with the pan 40.

It is, of course, noteworthy to state that the air gap between the primary and secondary pans serves to insulate these members and to prevent the transfer of cold.

from the primary pan to the secondary pan. This construction further precludes the tendency for condensate to form uponthe underside of the secondary pan.

It is to be noted (Fig. 2) that the core tubes are disposed. in checkerboard fashion consistent with the requirement that a maximum amount of primary surface area be exposed to drafts of air forced through the core in the direction of'thearrows.

Referring'now to Fig. 3 it is apparent that upon, intro -ducing fluid into the inlet chamber 19 the. fluid is free. to flow from left to right through the inlet group of. core-tubes 22 into the header 16 thence upwardly into the. outlet group of core tubes 23 into the outlet chamber 21' i and; back to. the source.

It is anticipated; that various'arrangements and representationsof'the present invention maybe undertaken without departing from the spirit and scope of the ap-.

pended'claim'.

I claim:

partition and overlying said opening, said cooling unit comprising a plurality of generally parallel core tubes, a

first header communicating with and supporting corresponding ends of said core tubes, a second header communicatingwith and-supporting the other ends of saidt core tubes; walls joining-the ends of said headers and.

amasss 6 References Cited in the file of this patent UNITED STATES PATENTS Miller Oct. 25, 1932 Harper Aug. 27, 1940 Ashley June 29, 1943 Pennella Feb. 5, 1946 Hull Oct. 21, 1952 Tanner May 1, 1956 

